INSPECTION PROCEDURE 9: Ambient temperature sensor system

  • When the ETACS-ECU of vehicles without KOS is replaced, the encrypted code of the ignition key needs to be registered to the ETACS-ECU. (If the encrypted code is not registered, the engine cannot be started. Register the encrypted code as described in Immobilizer System - How to Register Key ID .)


If the ambient temperature sensor system is defective, a malfunction may be present in the wiring harness between the ambient temperature sensor and the ETACS-ECU.


  • Malfunction of the ambient temperature sensor
  • Malfunction of the ETACS-ECU
  • Damaged wiring harness or connectors


STEP 1. Inspection of the ambient temperature sensor

Refer to .

Q. Is the A/C pressure sensor normal?

Go to Step 2.
Replace the ambient temperature sensor.

STEP 2. Check of open circuit in AMB+ and AMB- line (ETACS-ECU) between ambient temperature sensor connector and ETACS-ECU connector.

Q. Is the check result normal?

Go to Step 3.
Repair the connector(s) or wiring harness.

STEP 3. Check the data list below on the M.U.T.-III.

All the following items in the data list should be normal (Refer to ).
Item No.19: Ambient temperature sensor

Q. Is the check result normal?

Go to Step 4.
Replace the ETACS-ECU.

STEP 4. Retest the system.

Q. Is the check result normal?

Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace the ETACS-ECU.